docs: def _get_philny(self, C, mag):
          """
          Returns the intra-event random effects coefficient (phi)
          Equation 28.
          """
          if mag <= 4.5:
              return C["phi1"]
          elif mag >= 5.5:
              return C["phi2"]
          else:
              return C["phi2"] + (C["phi1"] - C["phi2"]) * (5.5 - mag)